1. The Field of the Invention
Phone plugs of the type concerned herein have electrically isolated conductive surfaces tandemly situated along a common axis. Of primary concern are two and three conductor type phone plugs having all points on the conductive surfaces equally spaced from the axis, whereby each contact will make electrical connection with its mating contact regardless of the angular disposition of the coupling part about the axis of engagement.
2. The Prior Art
Prior art phone plugs of the two conductor type generally have a conductive center contact pin concentrically situated within a hollow conductive cylinder and isolated from it by dielectric spacers. A common type has a pin in the form of a bolt which threads into a piece which forms the nose of the plug; the nose sits on a dielectric washer which isolates it from the end of the cylinder. The head of the bolt carries contact arms which are isolated from each other by a second dielectric washer; one arm is in electrical contact with the cylinder, the other is in electrical contact with the bolt. The arms are adapted for connection to electrical wires by soldering or screws; a sheath for protection of the arms and plug handling purposes is threaded to the conductive cylinder.
A common type of prior art three conductor plug is similarly assembled, with an additional hollow conductive cylinder between the nose and the first cylinder. This has a tubular extension which fits between the first cylinder and the center pin. Additional dielectric spacers and an additional contact arm are utilized.
The currently used phone plugs, including those described briefly above, are generally satisfactory in performance but involve a large number of parts and complicated manufacturing steps. Further, they do not lend themselves well to rapid assembly and are relatively expensive to make.